1. Field of the Invention
The present invention relates to an RFID (Radio Frequency IDentification) tag communications system including an RFID tag comprising an RFID chip and a tag antenna connected to the RFID chip.
2. Description of the Background Art
A system or a service using an RFID tag requires measures to protect itself against an illegal access of an unintended third person from reading or writing the tag information contained in the RFID tag or the like. Conventional RFID privacy protection technologies are described, for example, in Jun-ichi Kishigami, “All about Wireless IC Tags Directed to Ubiquitous Society—RFID Textbook” published by ASCII Corporation, Tokyo, Japan, pp. 165-184, 2005. This document describes three types of conventional RFID privacy protection technologies as briefly stated below.
One conventional RFID privacy protection technology is the Kill function. This technology disables an RFID tag to terminate its function once delivered to a consumer.
Another conventional RFID privacy protection technology is the internal re-encryption method. This technology makes an RFID tag equipped with the function of re-encrypting a public key cipher. An RFID tag is responsive to each delivery of a send request from an RFID reader to re-encrypt and send tag information such as tag identification (ID).
The remaining conventional RFID privacy protection technology is the Faraday cage. This technology prevents the illegal delivery of information such as tag identification from an RFID tag by covering the RFID tag with a material such as an aluminum foil that can shield radio waves.
The Kill function, however, suffers from problems in that the processing for disabling an RFID tag takes a long time, and the RFID tag, once disabled, cannot be used for services any more.
The internal re-encryption method needs to provide an RFID tag with means for encrypting tag information. The RFID tag then becomes more costly and the time per access becomes longer due to encryption or decryption.
For the Faraday cage, an RFID tag is required, every time to be accessed, to be taken out of and brought into its cover. This consumes time and cannot protect the RFID tag against an illegal access while it is out of the cover.